What is Air Leakage Testing

Building regulations from April 2006 require that new buildings comply with ‘Part L’. This means that a percentage of new dwellings need to undergo air tightness testing, air leakage testing or air permeability testing. 

Air tightness testing is the procedure to trace any unwanted drafts and uncontrolled airflow through the dwelling. Too much air leakage leads to heat loss resulting in higher C02 emissions. Reducing C02 emissions is the purpose of ‘Part L’ of the new building regulations through air tightness testing, air leakage testing and air permeability testing.

Zephyr Air Testing provides accredited air leakage test services and consultancy advice to Developers, Contractors and Sub Contractors, Architects and Designers, Housing Associations, Self Build Individuals and Construction Clients.

How it Works

Testing is done through a pressure test whereby fans are installed into a doorway of the building and used to create a measurable difference between the pressure inside and outside of the building. The amount of air needed to maintain this difference can be used to indicate the volume of air escaping through the fabric (what would be draughts in the building’s day-to-day life).

The results of the air leakage test are a key component of the calculation of the overall energy efficiency of the building and, therefore, achieving the necessary air tightness is a critical part of building control sign-off


In order to achieve increasingly challenging energy performance targets, air tightness requirements are becoming stricter. Typically, a good level of air tightness can still be achieved with excellent attention to detail in the decorative phase but, to achieve tighter targets, consideration must be given to air permeability within the design of the fabric, incorporating the use of membranes and tapes to maintain the air barrier.

Useful Guides from ATTMA

Please click the links below for ATTMA guidance and tips for temporary sealing and deciding whether you are ready to book an air tightness test.


Temp Sealing (Dwellings) Issue 3 - May 2017

Ready to Test (Dwellings) Issue 2 - May 2017

Please click the image blow to view Approved Document L1A: conservation of fuel and power in new dwellings, 2013 edition with 2016 amendments

Conservation of fuel and power Approved Document L1A